Effect of maldistribution and flow rotation on the shell side heat transfer in a shell and tube heat exchanger

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Abstract

A numerical analysis of flow maldistribution and shell side flow on heat in a shell
and tube heat exchanger is presented. The flow field at the inlet and in the headers was
obtained by solving conservation equations of mass and momentum by employing k-ε
turbulence model. As the flow maldistribution in the header affects the heat transfer
performance of the STHE, pressure drop and velocity distribution of the fluid inside the
header were analyzed. Two types of headers were considered with varying header length
for a Reynolds number range of 1000 to 3000. As the header length was increased to
1500 mm the flow maldistribution decreased and the static pressure was almost equal for
all the tubes in case of a conical header. Also, the numerical simulations show that the
conical header with 1500 mm header length has less flow maldistribution when compared
to other models. The Shell side flow was modeled as a flow along a twisted tube with a
diameter D and a length 30D using Catia V519. Four different models of the twisted tube
with pitch varying between 4D and 5.5D were studied for a range of Reynolds number Re
= 75-750. The analysis was carried out for three different wall temperatures of the twisted
tube such as 343 K, 363 K and 383 K. The pressure drop increased with increase in
Reynolds number, while the pressure drop and outlet fluid temperature increased with
decrease in the pitch of the tube. But the convective heat transfer decreased with
reduction in pitch. With a decrease in pitch, the energy transfer between the fluid and the
adjacent tubes increases resulting in increased outlet fluid temperature.

Description

Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering.